JAVA递归算法，1^2+2^2+3^2+....+n^2

publicclassDigui{//递归算法:publicstaticdoubledigui(intn){doublesum=0.0;if(n==1){sum=1;}else{if(n%2==0){sum=1.0/n+digui(n-1);}else{sum=-1.0/n+digui(n-1);}}returnsum;}//非递归算法：publicstaticdoublefeidigui(intn){doublecount=0.0;StringBuffersb=newStringBuffer();for(doublei=1;i<=n;i++){if(i==1){count=1;sb.append("n!="+n+"!=1");}else{if(i%2==0){count=count+1/i;sb.append("+1/"+(int)i);}else{count=count-1/i;sb.append("-1/"+(int)i);}}}System.err.println(sb.toString());returncount;}publicstaticvoidmain(String[]args){intn=10;doubledigui=feidigui(n);doublefeidigui=digui(n);System.out.println("递归算法："+n+"!="+digui);System.out.println("非递归算法："+n+"!="+feidigui);}}运行结果如下：n!=10!=1+1/2-1/3+1/4-1/5+1/6-1/7+1/8-1/9+1/10递归算法：10!=1.3543650793650797非递归算法：10!=1.3543650793650797